The principle aim of this ongoing project is to determine the mode of action on the mammalian (rat) nervous system of drugs known to produce psychotogenic or hallucinogenic effects in humans. Two main groups of psychotogenic drugs are under study: the "psychedelics" (e.g., LSD and psilocin) and the "amphetamines". An associated goal is to study the basic neurobiology of neurobiology of neuronal systems (e.g., serotonergic, noradrenergic, dopaminergic) upon which the psychotogenic drugs act. The principle methods employed are that of single-cell recording, microiontophoresis, and electrical stimulation of anatomically identified pathways. Work during the current year has included: (1) Studies on the effects of LSD and other psychotogenic drugs on the firing of neurons in the serotonergic system. (2) Studies on afferent inputs to serotonergic neurons of the raphe nuclei and noradrenergic neurons of the locus coeruleus. (3) Studies on the role of autoreceptors in mediating the effects of psychotogenic and other drugs on monoaminergic neurons. In general, the results show that psychotogenic drugs have powerful direct or indirect actions upon monoaminergic neurons; such actions may mediate the behavioral effects of these drugs.